1. Technical Field
The present invention relates to computer graphics. More specifically, the present invention relates to the selection of pixel density and image texture.
2. Description of Related Art
In computer graphics, the purpose of determining partials is to find the rate of change inside the texture map with respect to the current pixel being processed. Partials are the partial derivatives of the texture coordinates with respect to the screen coordinates. A texture map is an image stored in memory that is applied on a per-pixel basis to rendered primitives (graphics elements that are used as building blocks for creating images, such as a point, line, arc, cone or sphere). These partials are used to pick a Level of Detail (LOD) which has the closest rate of change to one.
Triangle partials are used by the rasterizing hardware to step in the x and y direction to render pixels to the frame buffer. Perspective correction generates nonlinear changes across the texture map so that the resulting image is in accordance to the view point being rendered. Normally the partials match the triangle partials, but if the texture coordinates are perspective corrected this is not true and the hardware has to perform a calculation on a per pixel basis to find the true partial.
Therefore, it would be desirable to have a method for generating partials for perspective corrected texture coordinates which requires fewer multiplies than the traditional method of calculating the partials for each pixel separately.